Winning
The mine comprises three pits: A-, B-, and C-pit. Operations started at A-pit in the 1950s. 2010.
aggregate. Traditionally an Iscor operation, the focus has predominantly been on metallurgical supply to the steel producers. However, over the past couple of years, the focus has shifted to the aggregate market, says Hattingh.“ There is a focus on growing the aggregate market for ready-mix and concrete blocks, among others.”
The nature of the reserve is interesting. One could almost draw a straight line down the middle of the three pits, with all the metallurgical material on the western side of the pit and all the aggregate material to the eastern side.
The most significant difference between metallurgical and aggregate product is the silica content. In metallurgical applications, the requirement is 3 % or less. If the silica material exceeds 3 %, it is classified as aggregate.
Currently the metallurgical products produce a silica content average of 1 – 1.5 %.
“ The focus for us is to continue metallurgical products, but then push the aggregate market to grow,” says Hattingh.
The mining and the processing of the two products are the same and it is almost impossible to differentiate between the products with the naked eye.“ When we drill in areas that we suspect have low silica content, we take the drill chippings to the lab, have it sampled, and confirm the quality. Therefore, we know if it’ s metallurgical or aggregate product before we blast. Some of our people have also worked in the quarry for years, and thus have experience in the geology.”
The plant produces approximately 1.5 – 1.6 million tonnes of product per year and moves another 250 000 – 300 000 tonnes of overburden. Additionally, it moves 100 000 tonnes of washed slimes material, bringing the total tonnages of material moved at Glen
Douglas mine to approximately two million tonnes per year.
Unique rail set-up
The plant comprises a primary circuit with a big Allis Chalmers gyratory crusher. The capacity of the plant is in excess of 1 000 tonnes per hour, but the operation is not currently running at full capacity.
The secondary plant consists of a washing plant with two Kawasaki cone crushers running at a capacity of 500 tonnes per hour.“ We are only running two shifts on the primary, secondary, and tertiary crushers, so there is additional shift hours available,” says Hattingh.
The feed from the secondary plant would go to either the aggregate stockpile or the metallurgical stockpile. The tertiary plant splits the metallurgical and aggregate product with a kidney conveyor.
The plant produces approximately 1.5 – 1.6 million tonnes of product per year and moves another 250 000 – 300 000 tonnes of overburden.
QUARRY SA | march 2017 _ 21